Radioimmunoassay

Radioimmunoassay (RIA) is a highly sensitive, quantitative laboratory technique that measures the concentration of a specific antigen — such as a hormone, drug, or pathogen-derived protein — in a biological sample by exploiting competitive binding between a radiolabelled antigen and the sample antigen for a limited supply of specific antibody. Developed in the late 1950s, RIA is widely used in veterinary science, endocrinology, pharmacology, and clinical diagnostics.